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A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head (centerfire ammunition) or at its rim (rimfire ammunition). Electrically-fired cartridges have also been made. Caseless ammunition has been made as well. A cartridge without a bullet is called a blank; one that is completely inert is called a dummy.

In popular use, the term "bullet" is often misused to refer to complete cartridges. This is incorrect; "bullet" refers specifically to the projectile itself, not the entire cartridge.

Design

.30-06 Springfield cartridge. This is a rimless cartridge case. Measurements are in inches.

The cartridge case seals a firing chamber in all directions except down the bore. A firing pin strikes the primer, igniting it. The spark from the primer ignites the powder. Burning gases from the powder expand the case to seal against the chamber wall. The projectile is then pushed in the direction that releases this pressure, down the barrel. After the projectile leaves the barrel the pressure is released, allowing the cartridge case to be removed from the chamber.

Automatic and semiautomatic firearms, which extract and eject the case automatically as a part of their operation, sometimes damage the case in the process of ejection. Brass is a commonly used material, as it is resistant to corrosion and ductile enough to be reformed and reloaded several times. However, some low-quality "plinking" ammunition, as well as some military ammunition (mainly from the former Soviet Union and China) is made with steel cases because steel is less expensive than brass. As militaries typically consider small arms cartridge cases to be a disposable, one-time-use affair, the lack of ductility is inconsequential for this application, although the mass of the case affects how much ammunition a soldier can carry. One downside caused by the lack of ductility is that a layer of carbon soot can blow around the steel casing into the chamber and make extraction of rounds difficult. This is less of a problem for weapons of the former Warsaw Pact nations, which were designed with much larger chamber tolerances than NATO weapons. Steel cases found in ammunition are often lacquered, or coated in a thin layer of polymer or copper (referred to as copper-washed) to protect the steel from corrosion. Some ammunition is also made with aluminum cases (see picture). Although more ductile than steel, the low tensile strength of aluminum cases prevents them from being reloaded.

Critical specifications include caliber, bullet weight, expected velocity, maximum pressure, headspace, overall length and primer type. A minor deviation in many of these specifications could result in damage to the firearm, and in extreme cases injury or death of the user. The diameter of a bullet is measured either as a decimal fraction of an inch, or in millimeters. The length of a cartridge case may also be designated in millimeters.

Where two numbers are together, the second number can contain a variety of meanings. Frequently the first is the diameter (caliber) of the cartridge, and the second is the length of the cartridge case. For example, the 7.62 x 51 mm uses a bore diameter of 7.62 mm and has an overall case length of 51 mm. In the case of old black powder cartridges, the second number typically refers to the powder charge. For example, the .50-90 Sharps is a .50 caliber bullet (.512) with a nominal charge of 90 grains (5.8 g) of black powder with a case length of 2.50 inches (64 mm).

One should be aware that cartridge nomenclature is inconsistent and unhelpful when trying to determine dimensions, tolerances or indeed almost any other characteristic of a given round. The .38 Special actually has a bullet diameter of 0.357 inches (9.1 mm) (jacketed) or 0.358 inches (9.1 mm) (lead) while the case has a diameter of 0.380 inches (9.7 mm). The .357 Magnum is a direct evolution of the .38 special, but differently named, and no reference is made to the longer case. The .30-06 rifle round is a (nominally) .30 inches (7.6 mm) caliber round designed in 1906; and the .303 British round may vary wildly in actual dimensions (as do the surviving rifle chambers of its era).

Most high-powered guns have relatively small bullets moving at high speeds. This is because while bullet energy increases in direct proportion to bullet weight, it increases in proportion to the square of bullet velocity. Therefore, a bullet going twice as fast has four times the energy (see physics of firearms). Bullet speeds are now limited by starting bore pressures, which in turn are limited by the strength of materials and the weight of gun people are willing to carry. Larger cartridges have more powder, and usually higher velocities.

Of the hundreds of different designs and developments that have occurred, essentially only two basic cartridge designs remain. All current firearms are either rimfire or centerfire. US military small arms suppliers are still trying to perfect electronic firing, which replaces the conventional firing pin and primer with an electrical ignition system wherein an electrical charge ignites the primer.

Centerfire

A centerfire cartridge has a centrally located primer, which in most US made ammunition, and in some (chiefly premium hunting and match ammunition) manufactured in other countries, can be replaced, so that the expensive brass cartridge case can be reused. Such a cartridge is said to be Boxer primed. Most European and Asian military ammunition uses a non-replaceable Berdan primer, which prevents the easy reuse of the case, because the anvil of the primer is an integral part of the case and can be deformed by firing. With care, it can be reloaded. An irregular fighter might more simply reload a Berdan-primed cartridge, since the new "primer" can be as simple as a bit of tin can and a match head, without the multi-stage process required for making a Boxer primer. US military ammunition is Boxer primed.

Rimfire

Rimfire cartridges, of which only the popular .22 LR remains in common use, were a popular solution before the centerfire design was fully perfected. They can only be used for fairly low powered cartridges, as the case has to be soft enough to be deformed by the firing pin, which detonates the priming compound in the rim. In the past, 9 mm cartridges were available, as well as .177, .25, etc. cartridges. BB and CB caps were common, as well as .22 Short and .22 Long.

Today, .22 LR (Long Rifle) accounts for much of rimfire ammunition shot. Recently, a .17 HMR (nominally .172 caliber) rimfire cartridge was released, and has become extremely popular among target shooters as well as small game hunters, due to its high velocity and flat shooting characteristics. .22 LR rounds normally use a soft lead bullet, and can be supersonic or subsonic. They are often copper-washed both for toxicity reasons and to prevent barrel fouling. .22 Magnum cartridges typically contain copper jacketed lead projectiles. The newer .17 rounds all feature bullets similar in construction to those found in centerfire cartridges, such as copper jacketed lead.

Semi-automatic vs. revolver cartridges

Nearly every semi-automatic pistol cartridge is "rimless", or more explicitly has an inset rim that the extractor engages. Revolver cartridges, on the other hand, have a rim at the base of the case which seats into the cylinder block to keep the cartridge from moving too far forward in the cylinder. Certain exceptions apply, namely for .45 ACP and 9mm Parabellum caliber rimless cartridges that are held in place at the inset with a half-moon clip, which keeps the otherwise flush bullets held within contact distance of the firing pin. For a visual comparison of similar-sized cartridges with different rims, see .380 ACP (semi-automatic) vs. .38 Special (revolver.)

Cartridges in use

There is great variety in the length and diameter of cartridges for the different kinds and calibers of rifles and pistols. The best cartridge for different purposes is subject to much discussion. However, there are standard uses for certain calibers, and these are a reliable guide to recommended uses.

It is important to note that equivalent caliber is by no means equivalent power. Generally speaking, "stopping power" is determined by the weight of the bullet, the terminal ballistics of the bullet – does it stay straight and in one piece, tumble, or "mushroom" on impact – and the charge of gunpowder accelerating it.

Jacketing of bullets

A cutaway showing a Japanese Navy 7.7 mm rimmed rounds as fired by the Type 92 and Type 97 machine guns - copies of Vickers and Lewis designs. The round is effectively interchangeable with .303 British

RNL - Round Nose Lead - An unjacketed lead bullet. Although largely supplanted by jacketed ammunition, this is still common for older revolver cartridges. Some hunters prefer roundnose ammunition for hunting in brush, because the bullet deflects less than sharp-nosed spitzer bullets, and long range is not required.[1]

WC - Wadcutter - Similar to the FNL, but completely cylindrical, in some cases with a slight concavity in the nose. This bullet derives its name from its popularity for target shooting, because the form factor cuts neat holes in paper targets, making scoring easier and more accurate.

AP - Armor Piercing - A hard bullet made from steel or tungsten alloys in a pointed shape typically covered by a thin layer of lead and/or a copper/brass jacket. The lead and jacket are intended to prevent barrel wear from the hard core materials. For metallic silhouette purposes, AP is slightly worse on unarmored targets than FMJ. This is to indicate the hard AP projectiles' tendency not to deform or reliably tumble/yaw.

FMJ - Full Metal Jacket - Made with a lead core surrounded by a full covering of brass, copper, or mild steel. These have very little deformation or expansion, but will occasionally yaw/tumble. Despite the name, a FMJ bullet typically has an exposed lead base, which is not visible in an intact cartridge.

TMJ - Total Metal Jacket - Featured in some Speer cartridges, the TMJ bullet has a lead core completely and seamlessly enclosed in brass, copper or other jacket metal, including the base. According to Speer literature, this prevents hot propellant gases from vaporizing lead from the base of the bullet, reducing lead emissions. Sellier & Bellot produce a similar version that they call TFMJ, with a separate end cap of jacket material.

JSP - Jacketed Soft Point - In the late 1800s, the Indian Army at Dum-Dum Arsenal, near Calcutta, developed a variation of the FMJ design where the jacket did not cover the nose of the bullet. The soft lead nose was found to expand in flesh while the remaining jacket still prevented lead fouling in the barrel. For metallic silhouette purposes, JSP is roughly splitting the difference between FMJ and JHP. It gives more penetration than JHP but has more stopping power than the FMJ.

JHP - Jacketed Hollow Point - Soon after the invention of the JSP, Woolwich Arsenal in Great Britain experimented with this design even further by forming a hole or cavity in the nose of the bullet while keeping most of the exterior profile intact. These bullets could theoretically deform even faster and expand to a larger diameter than the JSP. In personal defense use, concerns have arisen over whether clothing, especially heavy materials like denim, can clog the cavity of JHP bullets and cause expansion failures.

Glaser Safety Slug - The Glaser Safety Slug dates back to the early 1970s. The inventor, Colonel Jack Cannon named it for his friend Armin Glaser. Over the years, the projectiles have evolved from crude, hand-produced examples to mass-production; however, the basic concept has remained the same: copper jackets filled with bird shot and covered by a crimped polymer endcap. Upon impact with flesh, the projectile fragments, with the birdshot spreading like a miniature shotgun pattern. The standard "Blue" Glaser uses a rather fine birdshot which only gives 5 to 6 inches (130–150 mm) of penetration in flesh. The "Silver" Glaser adds another 1 to 2 inches (30–50 mm) of penetration with the use of slightly larger birdshot. Due to the much reduced penetration in flesh, some have theorized that the Glaser would be ideal where over-penetration of a projectile could be hazardous to bystanders. For instance, the Glaser may be stopped by an upraised arm. However, for the same reasons, the Glaser’s terminal performance can vary dramatically, producing impressive successes and equally spectacular failures depending on the angle at which the target is struck. Glancing hits on hard surfaces will result in fragmentation, reducing the risk of ricochets. However, the Glaser can penetrate barriers such as drywall, plywood, and thin sheet metal if struck directly.

The Hague Accords - The Hague Accords ban the use of expanding projectiles against the military forces of other nations. Some countries accept this as a blanket ban against the use of expanding projectiles against anyone, while others[2] use JSP and HP against non-military forces such as terrorists and criminals.

12 gauge/70 mm shotgun ammunition. They are listed from largest to smallest, separating the list into non-armor piercing and armor piercing types. The capacities are based on a 70 mm length hull.

Slug - Slugs may be made of solid lead, copper, or a composite. Slugs are stabilized in flight by rifling in the barrel, by means of integral rifling, or fin-stabilized. Solid or hollow-point slugs are available but, due to the relatively low velocity, hollow-point slugs have relatively low expansion. Baton - Rubber batons. Used for training.

000 Buck

- 8 lead pellets

(0.36 in/9.1 mm)

00 Buck

- 9 lead pellets

(0.33 in/8.4 mm)

0 Buck

- 12 lead pellets

(0.32 in/8.1 mm)

1 Buck

- 16 lead pellets

(0.30 in/7.6 mm)

4 Buck

- 27 lead pellets

(0.24 in/6.1 mm)

Calibers

Ammunition types are listed numerically.

.22 Long Rifle or .22LR cartridge is often used for target shooting and the hunting of small game such as squirrel, although because of its small size, self-defense handguns chambered in .22 rimfire (despite its name, it is often fired in pistols and revolvers in addition to rifles), though far less effective than centerfire handguns, can be concealed in situations where a larger handgun could not. It is the most commonly fired small arms cartridge, primarily because rimfire ammunition is much cheaper to produce than centerfire and because the recoil from the small .22" projectile being accelerated to relatively low velocities is very mild.

9 mm can refer to a variety of pistol cartridges, but most commonly refers to the 9x19mm Parabellum round. It is used in a variety of semi-automatic handguns and submachine guns.

.30 US Carbine - In 1940, the US Army's Ordnance Department approached Winchester with a light rifle concept. This was to bridge the difference between the .45 ACP and the .30-06. For the cartridge, Winchester recommended a rimless version of their .32 Winchester Self-Loading sized down for .308 inches (7.8 mm) projectiles. The resulting cartridge tossed a 110-grain (7.1 g) projectile at nearly 2,000 feet per second (610 m/s) from a carbine-length barrel.

.300 Whisper subsonic - Made by necking-up the .221 Remington Fireball case to .308 inches (7.8 mm) and using a 240-grain (16 g) Sierra MatchKing, this cartridge will fit and feed from 5.56x45mm NATO magazines. The Whisper is subsonic with about as much power and weight as .45 ACP, but in a thinner bullet which dramatically increases armor penetration.

.308 Winchester - the commercial name of a centerfire cartridge based on the military 7.62x51mm NATO round. Two years prior to the NATO adoption of the 7.62x51mm NATO T65 in 1954, Winchester (a subsidiary of the Olin Corporation) branded the cartridge and introduced it to the commercial hunting market as the .308 Winchester. Winchester's Model 70 and Model 88 rifles were subsequently chambered for the new cartridge. Since then, the .308 Winchester has become the most popular short-action big-game hunting cartridge worldwide. It is also commonly used for civilian targets, military sniping and police sharpshooting.

.338 Lapua (8.6x70mm or 8.58x71mm) - Originally designed as a long range sniping cartridge to bridge the ballistic gap between the .300 Winchester Magnum and the .50 BMG. It is a specialized rimless centerfire cartridge developed for sniper rifles. The .338 Lapua is a dual purpose anti-personnel and anti-materiel round for long-range shooting. In addition, with its increased popularity it is being used by big-game hunters and long-range competition shooters.

.338 Whisper subsonic - Made by necking-up the 7 mm Remington BenchRest case to .338 inches (8.6 mm) and using a 300-grain (19 g) Sierra MatchKing, this cartridge will fit and feed from 7.62x51mm NATO magazines.

.357 Magnum - Using a lengthened and strengthened version of the .38 Special case, the .357 Magnum was rapidly accepted by hunters and law enforcement. At the time of its introduction, it was claimed to easily pierce the body panels of automobiles and crack engine blocks.

.357 SIG - Designed to produce .357 Magnum revolver ballistics in a self-loading pistol, the .357 SIG is roughly a .40 S&W case necked down to .355 inches (9.0 mm).

.40 S&W subsonic - Roughly a shorter cased version of the 10x25mm Norma, this round loses about 20% of its energy when subsonic. This round is a step up in power from the 9x19mm subsonic, and has beaten out the parent 10x25mm subsonic in popularity.

.408 Chey Tac - is based on the .400 Taylor Magnum, which is based on a modified .505 Gibbs, necked down to 0.408 inches (10.36 mm).

.44 Magnum - A high powered pistol cartridge designed primarily for hunting.

.440 Cor-bon - The .440 Cor-bon is derived by necking down a .50 Action Express case down to accept the same .429-inch (10.9 mm) projectiles used in .44 Magnum cartridges. The 240-grain (16 g) .429-inch (10.9 mm) projectile has equal sectional density to the 325-grain (21.1 g) .500-inch (12.7 mm) of the .50 AE. However, with equal powder charges, the .440 Cor-bon can launch the 240-grain (16 g) projectile much faster than the 325 grains (21.1 g) projectile from the .50 AE. This equals greater energy and penetration against hard and soft targets.

.45 ACP - The standard US pistol round for about a century. Typical .45 ACP loads are subsonic, making them ideal for suppressed weapons.

.45 SAA - A more powerful .45 caliber round with a lengthened shell designed for the Colt Single Action Army. Other .45 caliber single action revolvers also chamber this round.

.45 Win Mag - Technically it is a .45 Winchester Magnum. The round was put on the market in 1979 and is basically like a .44 magnum in power but in size it would appear like a .45 ACP only longer and with a thicker rear to handle the greater pressures. The only current gun manufactured for this round is the Wildey.

.454 Casull - A very high powered pistol cartridge designed for taking the largest game animals.

.45-70 Government - Adopted by the US Army in 1873 as their standard service rifle cartridge. Most commercial loadings of the cartridge are constrained by the possibility that someone may attempt to fire a modern loading in one of the 1873-vintage rifles. However, current production rifles from Marlin, Ruger, and Browning can accept pressures nearly twice as high as the original black powder specs.

.50 Action Express (AE) - A very high powered pistol cartridge, exceeding the .44 Magnum, the cartridge's combination of high velocity and mass results in very favorable penetration characteristics against hard cover and certain types of body armor.

4.6x30mm H&K - H&K's answer to the 5.7x28mm FN. Based on H&K's experimental 4.6x36mm cartridge for the HK36 ACR in the early 1970s, even retaining its unique Löffelspitz (spoon-nose) projectile.

4.73x33mm H&K caseless - This revolutionary round, developed for Heckler & Koch G11, encases the bullet in a combustible material. There is no brass holding the cartridge together and the "powder" is completely burned upon firing.

5.56x45mm Steyr Flechette - Introduced for the US Army's ACR trials, the Steyr cartridge uses a plastic case with a small caliber flechette pulled by a 5.56 mm diameter sabot. The flechette is launched at a high velocity and the narrow projectile offers excellent penetration.

5.56x45mm NATO - Adopted by the US military in the 1960s, it later became the NATO standard assault rifle cartridge in the early 80s, displacing the 7.62x51mm. It is a military adaptation of the .223 Remington, a common cartridge for varminting and small game hunting.

5.7x28mm FN - The small high velocity cartridge appears much like a miniature rifle round. The 5.7 mm FN cartridge has amazing armor penetration due to its small projectile size and speed, yet has much less recoil than many pistol rounds.

7.62x39mm - The standard Soviet/ComBloc rifle cartridge from the mid-1940s to the mid-1970s, it is easily one of the most widely distributed cartridges in the world due to the distribution of the ubiquitous KalashnikovAK-47 series.

7.62x42mm - Outwardly similar to the Nagant revolver cartridge, the 7.62x42mm Soviet's case contains not only propellant and a projectile, but a piston sandwiched between the two. When the propellant is ignited, the expanding gas presses the piston forward to expel the projectile. However, the piston remains trapped inside the case, effectively sealing off the escape of propellant gas. The lack of expelled gas and a subsonic projectile results in no firing signature other than the mechanism of the parent weapon. The 7.62 × 42 mm is credited with a maximum effective range of 50 m, and the SP-4 armor-piercing cartridge can only defeat a helmet or body armor out to 25 m.

7.62x51mm NATO - This was the standard NATO rifle round until its replacement by the 5.56x45mm. It is currently NATO's standard sniper rifle and medium machine gun cartridge. In the 1950s it was the standard NATO cartridge for rifles, but recoil and weight proved problematic for the new battle rifle designs such as the FN FAL.

.30-06, (7.62x63mm) was the standard US Army rifle cartridge for the first half of the 20th century. It is a full-power rifle cartridge suitable for hunting most North American game.

7.62x54mmR - The standard Russian rifle round from the 1890s to the mid-1940s. The "R" stands for rimmed. The 7.62x54R rifle cartridge is a Russian design dating back to 1891. Originally designed for the Mosin-Nagant rifle, it was used during the late Tsarist era and throughout the Soviet period, in machine guns and rifles such as the SVT-40. The Winchester Model 1895 was also chambered for this cartridge per a contract with the Russian government. It is still in use by the Russian military in the Dragunov and other sniper rifles and some machine guns. The round is colloquially known as the "7.62 Russian". The name is sometimes confused with the "7.62 Soviet" round, which refers to the 7.62 × 39 cartridge used in the SKS and AK-47 rifles.

7.65x17mm Browning SR (.32 ACP) - A very small pistol round. However, it was the predominant police service cartridge in Europe until the mid-1970s. The "SR" stands for semi-rimmed, meaning cartridge case has small rim and usual groove.

7.92x57mm Mauser - The standard German service rifle cartridge from 1888 to 1945, the 7.92x57mm (aka 8 mm Mauser) has seen wide distribution around the globe through commercial, surplus, and military sales.

9x19mm Parabellum - Invented for the German military at the turn of the century, the wide distribution of the 9x19mm Parabellum cartridge made it the logical choice for the NATO standard pistol and SMG round.

9x21mm Russian - The 9x21mm Russian cartridge is roughly a lengthened version of the 9x18mm Makarov/PMM.

9x23mm Winchester - Roughly a 9x19mm case lengthened by 4 mm, the 9x23mm Winchester has its roots in IPSC competition shooting. John Ricco of CP Bullets had developed the '9x23mm Super' case as an alternative to the .38 Super ACP, whose cases varied dramaticly in strength. The .38 Super case also has the disadvantage of a vestigial semi-rim, which can interlock in magazines. Not to be confused with the externally similar 9x23mm Bergmann-Bayard (aka 9 mm Largo), Ricco's case could be safely loaded to nearly double the chamber pressure of the older cartridges. Since Olin/Winchester produced the cases for Ricco, they saw the commercial potential for using the case in a loaded cartridge. Unfortunately, Olin/Winchester tried to cut Ricco out of his potential royalties from sale of the new 9x23mm Winchester. The resulting lawsuit (won by Ricco) and the poor marketing of 9x23mm pistols by Colt has led to tepid commercial acceptance. Despite these troubles, the 9x23mm Winchester comes closer to the goal of matching .357 Magnum ballistics than the more popular .357 SIG.

9x30mm Grom - The 9x30mm Grom (Thunder) is roughly similar in dimensions and performance to the commercially unsuccessful 9 mm Winchester Magnum.

9x39mm Soviet subsonic - The 9x39mm Soviet is roughly a 7.62x39mm Soviet case necked up for a heavy 9 mm rifle projectile. There are competitive loadings from Nikolai Zabelin and Yuri Folov, each optimized for specific roles.

10x25mm Norma - Originally designed for the ill-fated Bren Ten pistol, the cartridge gained another lease on life when it was briefly promoted by the US FBI.

.50 BMG (12.7x99mm BMG) - Originally designed to pierce tank armor in the First World War, the cartridge still serves an anti-materiel round against light armor. It is used in heavy machine guns and high-powered sniper rifles. Such rifles are intended for destroying military matériel such as sensitive parts of grounded aircraft and armored transports. Civilian shooters use them for long-distance target-shooting.

12.7x108mm - The 12.7x108mm cartridge is a heavy machine gun and anti-materiel rifle cartridge used by the Soviet Union, the former Warsaw Pact, modern Russia, and other countries. It is the approximate Russian equivalent of the NATO .50 BMG (12.7x99mm NATO) cartridge. The differences between the two are the bullet shape, the types of powder used, and that the casing of the 12.7x108mm is 9 mm longer and marginally more powerful.

14.5x114mm - The 14.5x114 mm is a heavy machine gun and anti-materiel rifle cartridge used by the Soviet Union, the former Warsaw Pact, modern Russia, and other countries. It's most common use is in the KPV heavy machine gun which can be found on several Russian Military vehicles.

This cartridge was used with the muzzle-loading military firearm, the base of the cartridge being ripped or bitten off by the soldier, the powder poured into the barrel, and the bullet then rammed home. Before the invention of the firelock or flintlock, about 1635, the priming was originally put into the pan of the wheellock and snaphance muskets from a flask containing a fine-grained powder called serpentine powder.

The evolving nature of warfare required a firearm which could be fired more rapidly, resulting in the flintlock musket (and later the Baker rifle), in which the pan was covered by furrowed steel. This was struck by the flint and fired the weapon. In the course of loading a pinch of powder from the cartridge would be placed into the pan as priming, before the rest of the cartridge was rammed down the barrel, providing charge and wadding.

Later developments rendered this method of priming unnecessary, as, in loading, a portion of the charge of powder passed from the barrel through the vent into the pan, where it was held by the cover and hammer.

The next important advance in the method of ignition was the introduction of the copper percussion cap. This was only generally applied to the British military musket (the Brown Bess) in 1842, a quarter of a century after the invention of percussion powder and after an elaborate government test at Woolwich in 1834. The invention which made the percussion cap possible was patented by the Rev. A. J. Forsyth in 1807, and consisted of priming with a fulminating powder made of potassium chlorate, sulphur and charcoal, which exploded by concussion. This invention was gradually developed, and used, first in a steel cap, and then in a copper cap, by various gunmakers and private individuals before coming into general military use nearly thirty years later.

The alteration of the military flint-lock to the percussion musket was easily accomplished by replacing the powder pan by a perforated nipple, and by replacing the cock or hammer which held the flint by a smaller hammer with a hollow to fit on the nipple when released by the trigger. On the nipple was placed the copper cap containing the detonating composition, now made of three parts of potassium chlorate, two of fulminate of mercury and one of powdered glass. The detonating cap thus invented and adopted, brought about the invention of the modern cartridge case, and rendered possible the general adoption of the breech-loading principle for all varieties of rifles, shotguns and pistols. This greatly streamlined the reloading procedure and paved the way for semi- and fully-automatic firearms.

But this big leap forward came at a price. It introduced an extra component into each round – the cartridge case - which had to be removed before the gun could be reloaded. While a flintlock, for example, is immediately ready to be reloaded once it has been fired, adopting brass cartridge cases brought in the problem of extraction and ejection. The mechanism of a modern gun not only must load and fire the piece but also must remove the spent case, which may require just as many moving parts. Many malfunctions involve this process, either through failure to extract a case properly from the chamber or by allowing it to jam the action. Nineteenth-century inventors were reluctant to accept this added complication and experimented with a variety of self-consuming cartridges before finally accepting that the advantages of brass cases far outweighed their one drawback.

Integrated paper cartridges

The first integrated cartridge, was developed in Paris in 1808 by the Swiss gunsmith Jean Samuel Pauly in association with French gunsmith François Prélat. Pauly created the first fully self-contained cartridges:[4] the cartridges incorporated a copper base with integrated mercury fulminate primer powder (the major innovation of Pauly), a paper casing and a round bullet.[5] The cartridge was loaded through the breech and fired with a needle. The needle-activated central-fire breech-loading gun would become a major feature of firearms thereafter.[6] Pauly made an improved version which was protected by a patent on 29 September 1812.[4]

Probably no invention connected with firearms has wrought such changes in the principle of gun construction as those effected by the "expansive cartridge case". This invention has completely revolutionized the art of gunmaking, has been successfully applied to all descriptions of firearms, and has produced a new and important industry: that of cartridge manufacture. Its essential feature is preventing gas escaping the breech when the weapon is fired, by means of an expansive cartridge case containing its own means of ignition. Previous to this invention shotguns and sporting rifles were loaded by means of powder flasks and shot flasks, bullets, wads and copper caps, all carried separately. One of the earliest efficient modern cartridge cases was the pin-fire cartridge, developed by French gunsmith Casimir Lefaucheux in 1836.[7] It consisted of a thin weak shell made of brass and paper which expanded by the force of the explosion, fitted perfectly into the barrel, and thus formed an efficient gas check. A small percussion cap was placed in the middle of the base of the cartridge, and was exploded by means of a brass pin projecting from the side and struck by the hammer. This pin also afforded the means of extracting the cartridge case. This cartridge was introduced in England by Lang, of Cockspur Street, London, about 1845. Later in 1846, M.Houiller, another Paris gunsmith, improved on the system by introducing a fully metallic cartridge in 1847.[7]

A diagram of a Dreyse needle gun cartridge, showing the paper cartridge case, the sabot, and acorn-shaped bullet.

As a In the American Civil War (1861-65) a breechloading rifle, the Sharps, was introduced and produced in large numbers. It could be loaded with either a ball or a paper cartridge. After that war many were converted to the use of metal cartridges. The development by Smith and Wesson (amongst many others) of revolver handguns that used metal cartridges helped to establish cartridge firearms as the standard in the USA by the 1870s although many continued to use percussion revolvers well after that.

The first commercially successful all-metal cartridges were rimfire cartridges. The first of these was the .22 BB Cap, introduced around 1845. This was followed by the .22 Short in 1857. Larger caliber rimfires were soon introduced. Some of these were used in the American Civil War, including the .44 Henry and 56-56 Spencer. However, the large rimfires were soon replaced by centerfire cartridges, which could safely handle higher pressures.

In 1867 the British war office adopted the Eley-Boxer metallic central-fire cartridge case in the Enfield rifles, which were converted to Snider-Enfield breech-loaders on the Snider principle. This consisted of a block opening on a hinge, thus forming a false breech against which the cartridge rested. The priming cap was in the base of the cartridge, and was discharged by a striker passing through the breech block. Other European powers adopted breech-loading military rifles from 1866 to 1868, with paper instead of metallic cartridge cases. The original Eley-Boxer cartridge case was made of thin coiled brass - occasionally these cartridges could break apart and jam the breech with the unwound remains of the casing upon firing. Later the solid-drawn, central-fire cartridge case, made of one entire solid piece of tough hard metal, an alloy of copper, with a solid head of thicker metal, has been generally substituted.

Central-fire cartridges with solid-drawn metallic cases containing their own means of ignition are almost universally used in all modern varieties of military and sporting rifles and pistols.

Around 1870, machined tolerances had improved to the point that the cartridge case was no longer necessary to seal a firing chamber. Precision-faced bolts would seal as well, and could be economically manufactured.

Reloading

Some shooting enthusiasts reload their spent brass cartridges. By using a press and a set of dies, one can reshape, deprime, reprime, recharge the case with gunpowder, and seat and crimp a new bullet. One can do this at about half the cost of purchasing factory ammunition. It also allows one to use different weights and shapes of bullets, as well as varying the powder charge which affects accuracy and power. Enthusiasts usually only reload boxer primed cartridges as the process is more easily automated than berdan priming.

Caseless ammunition

An example of caseless ammunition. This disassembled round, the 4.73 x 33mm, is used in the Heckler & Koch G11 rifle.

In 1989, Heckler & Koch, a prominent German firearms manufacturer, began making press releases about the G11 assault rifle, which shot a 4.73x33 square caseless round. The round was mechanically fired, with an integral primer.

In 1993 Voere of Austria began selling a gun and caseless ammunition. Their system used a primer, electronically-fired at 17.5 ± 2 volts. The upper and lower limits prevent fire from either stray currents or static electricity. The direct electrical firing eliminates the mechanical delays associated with a striker, reducing reaction time (lock time), and allowing for easier adjustment of the rifle trigger.

In both cases, the "case" was molded directly from solid nitrocellulose, which is itself relatively strong and inert. The bullet and primer were glued into the propellant block.

Trounds

The Tround (Triangular Round) was a unique type of cartridge designed in 1958 by David Dardick, for use in specially designed Dardick 1100 and Dardick 1500 open-chamber firearms. As their name suggests, Trounds were triangular in cross-section, and were made of plastic or aluminium, with the cartridge completely encasing the powder and projectile. The Tround design was also produced as a cartridge adaptor, to allow conventional .38 Special and .22 Long Rifle cartridges to be used with the Dardick firearms.

Blank ammunition

A blank is a charged cartridge that does not contain a projectile — the opening where the projectile would be held is crimped shut or sealed with some material that will disperse rapidly upon leaving the barrel, in order to contain the propellant. This sealing material can still potentially cause harm at extremely close range. Blanks are used in training, but do not always cause a weapon to behave in an identical way to when using live ammunition; recoil will almost always be far weaker, and some automatic weapons will only cycle correctly when the weapon is fitted with a blank-firing adaptor to confine gas pressure within the barrel in order to operate the gas system. Blanks may also be used to launch a rifle grenade, although later systems used a "bullet trap" design that captures a bullet from a conventional round, speeding deployment. This also negates the risk of mistakenly firing a live bullet into the rifle grenade, causing it to explode instead of propelling it forward. Blanks may also be used in dedicated launchers for propelling a Grappling hook, rope line or flare, or for a training lure for training gun dogs. The propellant cartridges used in a heavier variety of nail gun are essentially rimfire blanks.

Drill rounds

Drill rounds are inert versions of cartridges used for education and practice during military training. Other than the lack of propellant, they are the same size as normal cartridges and will fit into the mechanism of a weapon in the same way as a live cartridge. To distinguish them from live rounds they are marked distinctively. Several forms of markings may be used; eg setting coloured flutes in the cartridge, drilling holes through the cartridge, colouring the bullet or cartridge, or a combination of these. In the case of centrefire drill rounds the primer will often be absent, its mounting hole in the base left open. Because they are mechanically identical to live rounds, which are intended to be loaded once, fired and then discarded, drill rounds have a tendency to become significantly worn and damaged with repeated passage through magazines and firing mechanisms, and need to be frequently inspected to ensure they are not so degraded as to become unusable - for example the casings can become torn or misshapen and snag on moving parts, or the bullet can become separated and stay in the breech when the cartridge is ejected.